Abstract

Objective: Literature review of the ergogenic aid β-hydroxy-β-methylbutyrate (HMB) and it effects on exercise-induced muscle damage.

Data sources: Medline, Ovid, SportDISCUS and relevant bibliographies were reviewed in February, 2007 using the following terms: HMB, beta-hydroxy-beta-methylbutyrate, muscle damage, CPK, creatine phosphokinase, exercise, delayed-onset muscle soreness.
Study selection: Relevant studies were limited to human investigations which were randomized, blinded, and placebo-controlled, and included an objective measurement of muscle damage. A total of eleven studies met the criteria for the review.
Data extraction: Relevant literature was identified and reviewed.
Data synthesis and conclusions: HMB is a nutritional supplement proposed to function as an anti-catabolic agent which decreases muscle protein breakdown and cell damage brought about by intense exercise. Previous research has claimed to support this hypothesis with findings of significantly reduced markers of muscle catabolism from HMB supplementation. Critical review of this literature reveals limitations in the assessments of these studies as evidenced by two main flaws in the basic premise behind HMB and muscle damage: (1) No rigorous scientific literature has verified the proposed mechanism through which HMB reduces muscle breakdown; (2) The use of muscle-specific enzymes is likely a labile and insensitive method to indicate muscle damage. Based on the literature to date, the effect of HMB on preventing exercise-induced muscle damage is likely transient and of little physiological significance. Further research to clarify the mechanism of HMB and precisely evaluate its role in protein turnover is needed.